Light emitting device and display device using the same

ABSTRACT

The disclosure relates to a light emitting device. The light emitting device includes an insulative transparent substrate, a light emitting material layer, and a metal metamaterial layer. The metal metamaterial layer is located between the insulative transparent substrate and the light emitting material layer. The metal metamaterial layer includes a number of periodically aligned metamaterial units. Because the plasmon of the metamaterial can control electromagnetic properties in nanoscale, light from the light emitting device can be polarized in nanoscale. Thus, the light emitting device can emit polarized light. The display device using the light emitting device is also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. §119 fromChina Patent Application No. 201410423957.7, filed on Aug. 26, 2014, inthe China Intellectual Property Office, disclosure of which isincorporated herein by reference.

FIELD

The subject matter herein generally relates to light emitting devicesand display devices, in particular, to light emitting devices anddisplay devices based on metamaterial.

BACKGROUND

Currently, liquid crystal displays (LCDs) are widely used.

Polarizer is used in the LCD to polarize the inputting light. Thepolarizer is a usually a film polarizer and will waste half of theincident light intensity. Thus, it not only reduces the brightness ofthe LCD but also waste the electric energy. Although an additionalliquid crystal layer is used to replace the polarizer to polarize theincident light. However, the polarizations of the incident light are allbased on far field operation.

What is needed, therefore, is to provide a light emitting device and adisplay device for solving the problem discussed above.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by wayof example only, with reference to the attached figures, wherein:

FIG. 1 is a schematic view of one embodiment of a light emitting device.

FIG. 2 is a cross-sectional view along line II-II of FIG. 1.

FIG. 3 shows a plurality of metamaterial units in different shapes.

FIG. 4 is a Scanning Electron Microscope (SEM) image of one embodimentof a metamaterial unit.

FIG. 5 shows how the light emitting device of FIG. 1 works byirradiating from the front surface and outputting light from the backsurface.

FIG. 6 is a polarization testing result of the light emitting device ofFIG. 1 on the work mode of FIG. 5.

FIG. 7 shows how the light emitting device of FIG. 1 works byirradiating from the back surface and outputting light from the frontsurface.

FIG. 8 is a polarization testing result of the light emitting device ofFIG. 1 on the work mode of FIG. 7.

FIG. 9 shows how a light emitting device of a compare embodiment works.

FIG. 10 is a polarization testing result of the light emitting device ofFIG. 9.

FIG. 11 shows testing results of transmission, reflection and absorptionof a metamaterial layer in a far field of another compare embodiment.

FIG. 12 is a schematic view of one embodiment of a display device.

FIG. 13 is a schematic view of another one embodiment of a lightemitting device.

FIG. 14 is a schematic view of another one embodiment of a lightemitting device.

FIG. 15 is an SEM image of one embodiment of a metamaterial unit.

FIG. 16 is a schematic view of another one embodiment of a lightemitting device.

FIG. 17 is a schematic view of another one embodiment of a lightemitting device.

FIG. 18 is a schematic view of another one embodiment of a lightemitting device.

FIG. 19 is a schematic view of another one embodiment of a lightemitting device.

FIG. 20 is a schematic view of another one embodiment of a lightemitting device.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures and components have notbeen described in detail so as not to obscure the related relevantfeature being described. The drawings are not necessarily to scale andthe proportions of certain parts may be exaggerated to better illustratedetails and features. The description is not to be considered aslimiting the scope of the embodiments described herein.

Several definitions that apply throughout this disclosure will now bepresented.

The term “coupled” is defined as connected, whether directly orindirectly through intervening components, and is not necessarilylimited to physical connections. The connection can be such that theobjects are permanently connected or releasably connected. The term“outside” refers to a region that is beyond the outermost confines of aphysical object. The term “inside” indicates that at least a portion ofa region is partially contained within a boundary formed by the object.The term “substantially” is defined to be essentially conforming to theparticular dimension, shape or other word that substantially modifies,such that the component need not be exact. For example, substantiallycylindrical means that the object resembles a cylinder, but can have oneor more deviations from a true cylinder. The term “comprising” means“including, but not necessarily limited to”; it specifically indicatesopen-ended inclusion or membership in a so-described combination, group,series and the like. It should be noted that references to “an” or “one”embodiment in this disclosure are not necessarily to the sameembodiment, and such references mean at least one.

References will now be made to the drawings to describe, in detail,various embodiments of the present light emitting devices and displaydevices based on metamaterial.

Referring to FIGS. 1-2, a light emitting device 100 of one embodimentincludes an insulative transparent substrate 110, a metamaterial layer120 and a light emitting layer 130. The insulative transparent substrate110, the metamaterial layer 120 and the light emitting layer 130 arestacked with each other.

The metamaterial layer 120 is located on a surface of the insulativetransparent substrate 110. The light emitting layer 130 is located on asurface of the metamaterial layer 120 so that the metamaterial layer 120is sandwiched between the insulative transparent substrate 110 and thelight emitting layer 130. The light emitting layer 130 covers themetamaterial layer 120. Furthermore, an optional transparent protectivelayer (not shown) can be located on a surface of the light emittinglayer 130 that is spaced from the metamaterial layer 120.

The insulative transparent substrate 110 can be flat or curved andconfigured to support other elements. The insulative transparentsubstrate 110 can be made of rigid materials such as silicon oxide,silicon nitride, ceramic, glass, quartz, diamond, plastic or any othersuitable material. The insulative transparent substrate 110 can also bemade of flexible materials such as polycarbonate (PC), polymethylmethacrylate acrylic (PMMA), polyimide (PI), polyethylene terephthalate(PET), polyethylene (PE), polyether polysulfones (PES), polyvinylpolychloride (PVC), benzocyclobutenes (BCB), polyesters, or acrylicresin. The size and shape of the insulative transparent substrate 110can be selected according to need. For example, the thickness of theinsulative transparent substrate 110 is in a range from about 100micrometers to about 500 micrometers. In one embodiment, the insulativetransparent substrate 110 is a silicon dioxide layer with a thickness of200 micrometers. If the metamaterial layer 120 and the light emittinglayer 130 is free standing, the insulative transparent substrate 110 isoptional.

The metamaterial layer 120 includes metamaterial which is artificialmaterial engineered to have properties that have not yet been found innature, such as negative refractive index. The metamaterial layer 120includes a plurality of metamaterial units 122 arranged to form aperiodic array. The plurality of metamaterial units 122 can be aplurality of bulges protruded from a surface of the insulativetransparent substrate 110 or a plurality of apertures/holes defined byand extending through the insulative transparent substrate 110. Theplurality of bulges are spaced from each other so that the metamateriallayer 120 allows light to pass through. The shapes of the plurality ofmetamaterial units 122 can be the patterns as shown in FIG. 3, or mirrorimage of the patterns of FIG. 3, or the patterns of FIG. 3 beingrotated. The patterns of the metamaterial units 122 of FIG. 3 can be

,

,

,

,

, and

.

The thickness h of the metamaterial units 122 can be in a range fromabout 30 nanometers to about 100 nanometers, the period of themetamaterial units 122 can be in a range from about 300 nanometers toabout 500 nanometers, and the line width of the metamaterial unit 122can be in a range from about 30 nanometers to about 40 nanometers. Thesize of the metamaterial unit 122 can be less than or equal towavelength of the light emitted from the light emitting layer 130. Inone embodiment, the size of the metamaterial unit 122 in each directionis less than 100 nanometers. The material of the metamaterial layer 120is metal which can generate surface plasmons (SPS). The metal can begold, silver, copper, iron, aluminum, nickel or alloys thereof. Themetamaterial layer 120 can be fabricated by treating a metal layer byfocusing ion beam etching or electron beam lithography. In oneembodiment, the metamaterial layer 120 is made by depositing a gold filmon the surface of the silicon dioxide layer and focusing ion beametching the gold film to obtain a plurality of strip-shaped aperturesarranged to form a periodic array. The plurality of strip-shapedaperture are used as the metamaterial units 122. The thickness of thegold film is 50 nanometers. The period of the strip-shaped apertures is250 nanometers. As shown in FIG. 4, the length of the strip-shapedaperture is 90.38 nanometers. The width of the strip-shaped aperture is26.53 nanometers. As shown in Table 1 below, the metamaterial unit 122can be classified into four categories according to the properties ofchirality symmetry, isotropy and polarized light. The metamaterial units122 of strip-shaped apertures are belong to category 4 of the Table 1.

TABLE 1 Chirality Categories Symmetry Isotropy Classification ofpolarized light 1 Yes Yes Circularly polarized light 2 Yes NoElliptically polarized light 3 No Yes Non-polarized light 4 No NoLinearly polarized light

The light emitting layer 130 includes photoluminescent material, such assemiconductor quantum dots, dye molecules or fluorescent powder. Thesemiconductor quantum dots can be PbS quantum dots, CdSe quantum dots orGaAs quantum dots. The diameter of the semiconductor quantum dot can bein a range from about 10 nanometers to about 200 nanometers. The dyemolecules can be rhodamine 6G. The light emitting layer 130 is locatedon a surface of the metamaterial layer 120 and extends through themetamaterial layer 120 to be in direct contact with the insulativetransparent substrate 110. The surface of the light emitting layer 130that is spaced from the metamaterial layer 120 can be flat or curved.The thickness H of the light emitting layer 130 can be in a range fromabout 50 nanometers to about 500 nanometers, such as from about 100nanometers to about 200 nanometers. The light emitting layer 130 can befabricated by spinning coating, spraying, printing, or depositing. Inone embodiment, the light emitting layer 130 includes a polymer matrix132 and a plurality of CdSe quantum dots 134 dispersed in the polymermatrix 132. The thickness of the light emitting layer 130 is 100nanometers. The light emitting layer 130 is made by dispersing the CdSequantum dots 134 in photoresist to form a mixture solution, and thenspinning coating the mixture solution on the metamaterial layer 120.

The surface of the light emitting layer 130 that is spaced from theinsulative transparent substrate 110 is defined as a front surface 102.The surface of the insulative transparent substrate 110 that is spacedfrom the light emitting layer 130 is defined as back surface 104. Asshown in FIG. 5, when the incident light 140 irradiate the lightemitting device 100 from the front surface 102, light emitted from thelight emitting layer 130 will pass through the metamaterial layer 120 tooutput from the back surface 104 to form the emitted light 150. Usually,the incident light 140 is laser light. As shown in FIG. 6, the degree oflinear polarization of the emitted light 150 from the back surface 104is 95%. As shown in FIG. 7, when the incident light 140 irradiate thelight emitting device 100 from the back surface 104, light emitted fromthe light emitting layer 130 will output from the front surface 102directly to form the emitted light 150. As shown in FIG. 8, the linearpolarization of the emitted light 150 from the front surface 102 is 10%.The linear polarization of the emitted light 150 of FIG. 5 is muchgreater than the linear polarization of the emitted light 150 of FIG. 7.When the emitted light 150 pass through the metamaterial layer 120, thelinear polarization of the emitted light 150 is enhanced.

Usually, a light source with a distance far than a wavelength can beseen as a far field light source, and a light source with a distanceclose to 1/10 wavelength can be seen as a near field light source. Thewavelength of visible light is in a range from about 390 nanometers toabout 770 nanometers. Usually, the electromagnetic field is localized inthe subwavelength scale near the surface of the metamaterials.Therefore, the light emitting layer 130 of visible light with athickness less than 100 nanometers is within the near field domain ofthe metamaterial layer 120, which guarantees the strong interactionbetween the metamaterial layer 120 and the light emitting layer 130.

The metamaterial layer 120 can be regarded as a nano antenna array forthe electromagnetic waves and will cause scattering to theelectromagnetic waves nearby. According to the classical electromagnetictheory the electromagnetic waves that were previously emitted by thedipole sources undergo a series of scattering events on the antennaelements, which would rebound back and, in turn, work as the drivingfield for the dipole moments. Secondary emission would be induced, whichinfluences the total emission fields through superimposing on thepreviously emitted fields. Notably, the secondary emitted field ispolarized identically to the scattering driving fields. In oneembodiment, the metamaterial layer 120 of FIG. 1 show differentscattering strengths for orthogonally polarizations, the scatteringalong Y-direction could be enhanced, whereas the scattering fields alongthe X-direction is overwhelmed. As a result, the linearly Y-polarizedemission in the far-field happens. According to the Fresnel rule and theboundary conditions of electromagnetic fields, the emitted light 150 onthe back surface 104 has higher polarization.

Furthermore, as shown in FIGS. 9-10, in one compare embodiment, thelight emitting layer 130 is directly located on a surface of theinsulative transparent substrate 110 without any metamaterial layertherebetween. When the incident light 140 irradiate the light emittinglayer 130 from the front surface 102, the emitted light 150 from theback surface 104 is non-linearly polarized light. Thus, the polarizationproperty of the light emitting device 100 is caused by the metamateriallayer 120.

In another compare embodiment, the transmission, reflection andabsorption of the metamaterial layer 120 are tested when a far fieldplane wave light source is used to irradiate the light emitting device100. The far field plane wave light source emits white light, whichwould not activate the light emitting layer 130 to emit light, toirradiate the light emitting device 100 from front side 102. As shown inFIG. 11, Ty/Tx is about 5, where the Ty represents the transmission ofthe Y polarized light of the emitted light 150 and Tx represents thetransmission of the X polarized light of the emitted light 150. Thelinear polarization of the transmission light can be calculated by(I_(max)−I_(min))/(I_(max)+I_(min))=(5−1)/(5+1)˜67%. Therefore, thepolarization of the metamaterial layer 120 for far field light source isabout 67%, but for near field light source is about 95%. Therefore, thepolarization of the emitted light 150 of the light emitting device 100is not caused simply by the transmission of the metamaterial layer 120,but caused by that the metamaterial layer 120 adjust the radiation rateof the light emitting layer 130 which is a near field light source.

The light emitting device 100 has following advantages. First, thebrightness of the emitted light 150 can be enhanced because the plasmonresonance of the metamaterial layer 120. Second, the light emitted fromthe light emitting layer 130 are polarized in nano-scale by thepolarization of plasmon resonance of the metamaterial layer 120 so thatthe light emitting device 100 can emit polarized light directly.

Referring to FIG. 12, a display device 10 is provided. The displaydevice 10 includes the light emitting device 100, a light guide plate160 and a liquid crystal panel 170. The light emitting device 100, thelight guide plate 160 and the liquid crystal panel 170 are stacked witheach other in that order. The light guide plate 160 is located on theback surface 104 of the insulative transparent substrate 110 andsandwiched between the light emitting device 100 and the liquid crystalpanel 170. The light emitting device 100 is used as a light source ofthe display device 10. Because the light emitting device 100 can emitpolarized light directly, the display device 10 is simple and does notneed other polarizer. The display device 10 can also include the lightemitting devices 200, 300, 400 of embodiments below.

Referring to FIG. 13, a light emitting device 200 of one embodimentincludes the insulative transparent substrate 110, the metamateriallayer 120, the light emitting layer 130 and a reflection layer 180. Theinsulative transparent substrate 110, the metamaterial layer 120, thelight emitting layer 130 and the reflection layer 180 are stacked witheach other.

The light emitting device 200 is similar with the light emitting device100 except that the reflection layer 180 is located on and covers thelight emitting layer 130 so that the light emitting layer 130 issandwiched between the insulative transparent substrate 110 and thereflection layer 180. The reflection layer 180 can be a metal film suchas a gold film. Because part of the light that is emitted from the lightemitting layer 130 and travel to the reflection layer 180 will bereflected by the reflection layer 180 to pass through the metamateriallayer 120 to output from the back surface 104, the light emittingefficiency of the light emitting device 200 is enhanced.

In work of the light emitting device 200, the incident light 140 canirradiate the light emitting device 200 from the back surface 104 orside surface 106. The emitted light 150 output from the back surface104. In one embodiment, the incident light 140 irradiate the lightemitting device 200 from entire side surface 106 so that more emittedlight 150 can output from the back surface 104.

Referring to FIG. 14, a light emitting device 300 of one embodimentincludes the insulative transparent substrate 110, the metamateriallayer 120, and the light emitting layer 130. The insulative transparentsubstrate 110, the metamaterial layer 120, and the light emitting layer130 are stacked with each other.

The light emitting device 300 is similar with the light emitting device100 except that the metamaterial layer 120 includes a plurality ofstrip-shaped bulges arranged to form a periodic array and used as aplurality of metamaterial units 122. The metamaterial layer 120 defineda plurality of spaces 124 between adjacent metamaterial units 122. Thelight emitting layer 130 is wave-shaped and has a uniform thickness. Thelight emitting layer 130 has a plurality of first surfaces and aplurality of second surface depressed from the plurality of firstsurfaces. As shown in FIG. 15, the plurality of metamaterial units 122are arranged to form a two dimensional array. In one embodiment, thethickness of the strip-shaped bulges is 50 nanometers, the period of thestrip-shaped bulges is 300 nanometers, the length of the strip-shapedbulge is 152 nanometers, and the width of the strip-shaped bulge is 116nanometers.

Referring to FIG. 16, a light emitting device 400 of one embodimentincludes the insulative transparent substrate 110, the metamateriallayer 120, and the light emitting layer 130. The insulative transparentsubstrate 110, the metamaterial layer 120, and the light emitting layer130 are stacked with each other.

The light emitting device 400 is similar with the light emitting device100 except that the plurality of metamaterial units 122 are a pluralityof

shaped apertures arranged to form a periodic two dimensional array. Theplurality of

shaped apertures is fabricated by etching a gold film. In oneembodiment, the thickness of the gold film is 50 nanometers, the periodof the

shaped apertures is 400 nanometers, and the line width of the

shaped aperture is 40 nanometers.

The light emitting devices 100, 200, 300, 400 are all optical pumpinglight emitting devices and work by light irradiating. The light emittingdevices 500, 600, 700, 800 below are electric pumping light emittingdevices and work by supplying a voltage or current.

Referring to FIG. 17, a light emitting device 500 of one embodiment is avertical structure light emitting diode (LED) and includes a firstelectrode 510, a first semiconductor layer 520, an active layer 530, asecond semiconductor layer 540 and a second electrode 550.

The first electrode 510, the first semiconductor layer 520, the activelayer 530, the second semiconductor layer 540 and the second electrode550 are stacked with each other in that order. The first electrode 510is electrically connected to the first semiconductor layer 520. Thesecond electrode 550 is electrically connected to the secondsemiconductor layer 540. At least one of the first electrode 510 and thesecond electrode 550 is a metal metamaterial layer, and the distancebetween the metal metamaterial layer and the active layer 530 is lessthan or equal to 100 nanometers. In one embodiment, the distance betweenthe metal metamaterial layer and the active layer 530 is less than orequal to 50 nanometers. The active layer 530 can be seen as a near fieldlight source of the metal metamaterial layer.

If the first semiconductor layer 520 is an N-type semiconductor, thesecond semiconductor layer 540 is a P-type semiconductor, and viceversa. The N-type semiconductor layer provides negative electrons, andthe P-type semiconductor layer provides positive holes. The N-typesemiconductor layer can be made of N-type gallium nitride, N-typegallium arsenide, or N-type copper phosphate. The P-type semiconductorlayer can be made of P-type gallium nitride, P-type gallium arsenide, orP-type copper phosphate. The first semiconductor layer 520 can have athickness of about 50 nanometers to about 3 micrometers. The secondsemiconductor layer 540 can have a thickness of about 50 nanometers toabout 3 micrometers. If the first electrode 510 is a metal metamateriallayer, the thickness of the first semiconductor layer 520 should be lessthan 50 nanometers so that the distance between the first electrode 510and the active layer 530 is less than 50 nanometers. If the secondelectrode 550 is a metal metamaterial layer, the thickness of the secondsemiconductor layer 540 should be less than 50 nanometers so that thedistance between the second electrode 550 and the active layer 530 isless than 50 nanometers.

The active layer 530 is sandwiched between the first semiconductor layer520 and the second semiconductor layer 540. The active layer 530 is aphoton exciting layer and can be one of a single quantum well layer ormultilayer quantum well films. The active layer 530 can be made ofgallium indium nitride (GaInN), aluminum indium gallium nitride(AlGaInN), gallium arsenide (GaSn), aluminum gallium arsenide (AlGaSn),gallium indium phosphide (GaInP), or aluminum gallium arsenide (GaInSn).The active layer 530, in which the electrons fill the holes, can have athickness of about 0.01 micrometers to about 0.6 micrometers.

The first electrode 510 may be a P-type or an N-type electrode and isthe same type as the first semiconductor layer 520. The second electrode550 may be a P-type or an N-type electrode and is the same type as thesecond semiconductor layer 540. The thickness of the first electrode 510can range from about 0.01 micrometers to about 2 micrometers. Thethickness of the second electrode 550 can range from about 0.01micrometers to about 2 micrometers. The material of the first electrode510 and the second electrode 550 is metal such as gold, silver, copper,iron, aluminum, nickel, titanium, or alloys thereof.

In one embodiment, the first semiconductor layer 520 is an N-typegallium nitride layer with a thickness of 0.3 micrometers, and thesecond semiconductor layer 540 is a P-type gallium nitride layer with athickness of 100 nanometers, and the active layer 530 includes a GaInNlayer and a GaN layer stacked with each other and has a thickness ofabout 0.03 micrometers. The first electrode 510 is N-type electrode andincludes a nickel layer and a gold layer. The thickness of the nickellayer is about 15 nanometers. The thickness of the gold layer is about200 nanometers. The second electrode 550 is P-type electrode andincludes a metal metamaterial layer having the same pattern as themetamaterial layer 120 of FIG. 16 and a thickness of 100 nanometers.

In work, a voltage is supplied to the light emitting device 500 throughthe first electrode 510 and the second electrode 550. The active layer530 is activated to produce photons. The photons output from the secondelectrode 550. Because the second electrode 550 is a metal metamateriallayer spaced from the active layer 530 with a distance less than 100nanometers, the light emitting rate of the active layer 530 can beenhanced by the plasmons of the metal metamaterial layer. Furthermore,the light emitting device 500 can emit polarized light directly becauseof the polarization of the metal metamaterial layer.

In anther embodiment, both the first electrode 510 and the secondelectrode 550 is metal metamaterial layer, and both the firstsemiconductor layer 520 and the second semiconductor layer 540 hasthickness less than 100 nanometers. The photons produced from the activelayer 530 can output from both the first electrode 510 and the secondelectrode 550.

Referring to FIG. 18, a light emitting device 600 of one embodiment is avertical structure LED and includes a reflection layer 580, a firstelectrode 510, a first semiconductor layer 520, an active layer 530, asecond semiconductor layer 540 and a second electrode 550.

The light emitting device 600 is similar with the light emitting device500 except that a reflection layer 580 is located on a surface of thefirst electrode 510 that is spaced from the first semiconductor layer520. The reflection layer 580 covers the first electrode 510. Becausepart of the light that is emitted from the active layer 530 and travelto the reflection layer 580 will be reflected by the reflection layer580 to pass through, be polarized and enhanced by the metal metamateriallayer of the second electrode 550, the light emitting efficiency of thelight emitting device 600 is enhanced.

Referring to FIG. 19, a light emitting device 700 of one embodiment is ahorizontal structure LED and includes a substrate 560, a first electrode510, a first semiconductor layer 520, an active layer 530, a secondsemiconductor layer 540 and a second electrode 550.

The light emitting device 700 is similar with the light emitting device500 except that part of the first semiconductor layer 520 is exposed toform an exposed part, and the first electrode 510 is located on theexposed part of the first semiconductor layer 520. In one embodiment,the substrate 560, the first semiconductor layer 520, the active layer530, the second semiconductor layer 540 and the second electrode 550 arestacked with each other in that order. The area of the active layer 530,the second semiconductor layer 540 and the second electrode 550 are thesame and smaller than that of the first semiconductor layer 520 so thatpart of the first semiconductor layer 520 is exposed. The secondelectrode 550 is a metal metamaterial layer spaced from the active layer530 with a distance less than 100 nanometers.

Referring to FIG. 20, a light emitting device 800 of one embodiment is aLED and includes a first electrode 510, a first semiconductor layer 520,an active layer 530, a second semiconductor layer 540, a secondelectrode 550 and a metal metamaterial layer 570.

The light emitting device 800 is similar with the light emitting device500 except the metal metamaterial layer 570. The metal metamateriallayer 570 is located on a side surface of the light emitting device 800that is perpendicular with each of the first electrode 510, the firstsemiconductor layer 520, the active layer 530, the second semiconductorlayer 540, and the second electrode 550. In one embodiment, the lightemitting device 800 is a cuboid and has four side surfaces. The metalmetamaterial layer 570 is located on only one of the four side surfaces.The other three side surfaces can also be coated with metal reflectionfilms. The first electrode 510 and the second electrode 550 can also bea metal metamaterial layer. The metal metamaterial layer 570 has apattern same as that of the metamaterial layer 120 of FIG. 1. Becausethe metal metamaterial layer 570 is in direct contact with the activelayer 530, the photons produced from the active layer 530 and outputfrom the metal metamaterial layer 570 on the side surface can beenhanced and polarized by the metal metamaterial layer 570. Thus, thelight emitting device 800 has an enhanced brightness and can emitpolarized light directly.

The embodiments shown and described above are only examples. Even thoughnumerous characteristics and advantages of the present technology havebeen set forth in the foregoing description, together with details ofthe structure and function of the present disclosure, the disclosure isillustrative only, and changes may be made in the detail, including inmatters of shape, size and arrangement of the parts within theprinciples of the present disclosure up to, and including, the fullextent established by the broad general meaning of the terms used in theclaims.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. The description and the claims drawn to a method may includesome indication in reference to certain steps. However, the indicationused is only to be viewed for identification purposes and not as asuggestion as to an order for the steps.

What is claimed is:
 1. A light emitting device, comprising an insulativetransparent substrate and a light emitting layer located on theinsulative transparent substrate, wherein a metal metamaterial layer issandwiched between the insulative transparent substrate and the lightemitting layer, and the metal metamaterial layer comprises a pluralityof metamaterial units arranged to form a periodic array.
 2. The lightemitting device of claim 1, wherein the plurality of metamaterial unitsare chirality symmetry and isotropy.
 3. The light emitting device ofclaim 1, wherein the plurality of metamaterial units are chiralitysymmetry and not isotropy.
 4. The light emitting device of claim 1,wherein the plurality of metamaterial units are neither chiralitysymmetry nor isotropy.
 5. The light emitting device of claim 1, whereina thickness of each of the plurality of metamaterial units is in a rangefrom about 30 nanometers to about 100 nanometers, a period of theplurality of metamaterial units is in a range from about 300 nanometersto about 500 nanometers, and a line width of each of the plurality ofmetamaterial units is in a range from about 30 nanometers to about 40nanometers.
 6. The light emitting device of claim 1, wherein the metalmetamaterial layer defines a plurality of apertures to expose parts ofthe insulative transparent substrate, and the light emitting layer arein direct contact with the insulative transparent substrate by extendingthrough the plurality of apertures.
 7. The light emitting device ofclaim 1, wherein the light emitting layer is wave-shaped and has auniform thickness.
 8. The light emitting device of claim 1, whereinmaterial of the metal metamaterial layer is selected from the groupconsisting of gold, silver, copper, iron, aluminum, nickel and alloysthereof.
 9. The light emitting device of claim 1, further comprising areflection layer located on and covers the light emitting layer so thatthe light emitting layer is sandwiched between the insulativetransparent substrate and the reflection layer.
 10. A light emittingdevice, comprising a light emitting layer, wherein a metal metamateriallayer is located on the light emitting layer, and the metal metamateriallayer comprises a plurality of metamaterial units arranged to form aperiodic array.
 11. The light emitting device of claim 10, wherein theplurality of metamaterial units are chirality symmetry and isotropy. 12.The light emitting device of claim 10, wherein the plurality ofmetamaterial units are chirality symmetry and not isotropy.
 13. Thelight emitting device of claim 10, wherein the plurality of metamaterialunits are neither chirality symmetry nor isotropy.
 14. The lightemitting device of claim 10, wherein a thickness of each of theplurality of metamaterial units is in a range from about 30 nanometersto about 100 nanometers, a period of the plurality of metamaterial unitsis in a range from about 300 nanometers to about 500 nanometers, and aline width of each of the plurality of metamaterial units is in a rangefrom about 30 nanometers to about 40 nanometers.
 15. A display device,comprising a light emitting device, a light guide plate and a liquidcrystal panel, wherein the light emitting device comprises an insulativetransparent substrate, a light emitting layer located on the insulativetransparent substrate, and a metal metamaterial layer sandwiched betweenthe insulative transparent substrate and the light emitting layer; themetal metamaterial layer comprises a plurality of metamaterial unitsarranged to form a periodic array.
 16. The display device of claim 15,wherein the plurality of metamaterial units are chirality symmetry andisotropy.
 17. The display device of claim 15, wherein the plurality ofmetamaterial units are chirality symmetry and not isotropy.
 18. Thedisplay device of claim 15, wherein the plurality of metamaterial unitsare neither chirality symmetry nor isotropy.
 19. The display device ofclaim 15, wherein a thickness of each of the plurality of metamaterialunits is in a range from about 30 nanometers to about 100 nanometers, aperiod of the plurality of metamaterial units is in a range from about300 nanometers to about 500 nanometers, and a line width of each of theplurality of metamaterial units is in a range from about 30 nanometersto about 40 nanometers.